Relation of magnetic properties of the rocks of the Ukrainian Shield to their composition and metamorphism

Abstract

A magnetization map has been compiled for the Ukrainian Shield. The magnetization contours generally resemble those for the anomalous magnetic field, and this is explained by the coincidence of the directions of the induced and remanent magnetizations for most of the shield rocks.The magnetization map makes it possible to establish a correlation between the magnetization distribution in the shield rocks and the history of evolution and peculiarities of the structural blocks of the shield.The sum magnetizations of the large blocks range from 100 to 550 × 10−3 A m−1. A high magnetization (800–3000 × 10−3 A m−1) is characteristic of the regions composed of the products of metamorphism and granitization of the oldest Early Archean magmatic formations. In these areas regional magnetic anomalies are revealed.In order to study the physical properties and mineral composition of rocks within the areas of two regional anomalies, correlation of magnetization with original composition and degree of metamorphism and granitization has been investigated.The data obtained make it possible to predict the magnetization of the lower crust and to use the magnetic field data in constructing a complex geophysical model for the earth's crust.